Fix localization file loading, and introduce the load_textdomain() method

As pointed out by aarcos in the forums
(http://wordpress.org/support/topic/translation-files-not-loading-and-suggested-patch-code#post-4754557),
localization files are not loading correctly, due to an invalid path argument.

Fix loading by correcting the path, and add more locations to check.
This allows users to add custom translation files that won't be stomped
out when the plugin is updated. Introduce the load_textdomain() method
to handle the more verbose setup.

git-svn-id: http://plugins.svn.wordpress.org/edit-author-slug/trunk@824522 b8457f37-d9ea-0310-8a92-e5e31aec5664
Update tested to tag

git-svn-id: http://plugins.svn.wordpress.org/edit-author-slug/trunk@824524 b8457f37-d9ea-0310-8a92-e5e31aec5664
Fix text domain loading once and for all

git-svn-id: http://plugins.svn.wordpress.org/edit-author-slug/trunk@824526 b8457f37-d9ea-0310-8a92-e5e31aec5664
Update pot and version info

git-svn-id: http://plugins.svn.wordpress.org/edit-author-slug/trunk@824539 b8457f37-d9ea-0310-8a92-e5e31aec5664
Brace yo'self fool, and mind ya own d**n business!

* Add empty index.php files to prevent snooping for those who haven't turned off indexes
* Add braces where appropriate to come in line with coding standards. Don't want our pants falling down!

git-svn-id: http://plugins.svn.wordpress.org/edit-author-slug/trunk@825894 b8457f37-d9ea-0310-8a92-e5e31aec5664